Lightweight conveyor roller

ABSTRACT

A roller made lighter through the use of lightening elements. The inventive roller, with its lightening element(s), is lighter yet maintains its overall dimensions, is strong and durable enough to withstand the rigors of the transportation industry and/or is cost effective to produce and maintain. The lightweight roller may be part of a system having at least one operable roller unit, each roller unit having a roller, cylindrical in shape having a length and a diameter, and a center aperture extending through the length of the roller, an axel/shaft having a diameter sized to rotatably fit within the central aperture of the roller, the shaft further having a retention mechanism located upon the shaft ends and an elongate “U” shaped roller rack, the roller rack sized to extend the length of the roller and having a pair of upwardly extending arms located adjacent the ends of the roller, each arm end having an aperture sized to receive the respective shaft end and locate the shaft with the roller in a fixed location. The roller system has at least one roller, preferably more or all of the rollers, having internal and/or external lightening elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/872,732,filed Apr. 29, 2013, which application is a continuation of applicationSer. No. 12/386,776, filed Apr. 22, 2009, now U.S. Pat. No. 8,430,801,which application claims the benefit of provisional application Ser. No.61/125,043, filed Apr. 22, 2008, which applications are incorporatedherein by reference in their entirety.

The present invention relates to lightweight rollers for conveyors. Inone aspect, the rollers have a high strength to weight ratio. In anotheraspect, these rollers can be easy to manufacture, easy to use,economical to produce, and/or highly cost effective.

BACKGROUND

Conveyors are used in various systems, including manufacturing plants,loading and unloading areas such as shipping and receiving docks, andcargo haulers, such as aircrafts, boats, trains and trucks. While someconveyors may have an extending belt which provides the carryingsurface, many do not. Conveyors for large or packaged goods often do nothave large belts and merely rely on a series of rollers to carry theproduct along a production line.

One of the biggest factors in transporting goods by cargo haulers is thecost of fuel. Recently, the price for a barrel of oil has fetched wellover $100 a barrel. These fuel costs can cut deeply into profits. Itwould, therefore, be desirable to reduce fuel consumption, thereby,increasing profits. One way to achieve this is to reduce the weight ofthe transporting vehicle. A lighter transporting vehicle will consumeless fuel. Alternatively, a lighter transporting vehicle can carry morecargo for the same amount of fuel consumed.

In the case of transporting vehicles that carry their conveyor systemsonboard, one way to lighten the vehicles is to decrease the weight ofthe rollers on the conveyor system. For example, in the airlineindustry, the placement of the roller can be in the cargo bay of anaircraft to allow the loading, unloading, and placement of cargopackages within the aircraft. The rollers in the cargo bay perform thedual function of allowing the cargo containers to be rolled into placeand supporting the cargo during flight. An exemplary aircraft may haveanywhere between 100 to 3000 rollers. It has been posited by some in thefield that a roller reduced by as little as ½ a gram or about 0.018ounces can make a beneficial impact on fuel consumption over the lengthof its air travel life.

Reducing the weight of rollers may be one crucial way to save on fuelcosts; however, the rollers must still be able to perform their intendedfunction. While this goes without saying in all areas of roller use,maintaining the integrity of the roller and still reducing weight isespecially difficult in the area of transportation by aircraft. Airtravel requires special consideration such as being able to withstandrapid fluctuations in temperature and pressure many times during aflight. The effect of G force, or gravitational force, on the loads thatthe rollers may bear must be taken into consideration as the aircraftcan go through rapid changes in altitude during flight. Also, air travelpresents unique safety issues requiring maximum burn rates andcomparison tests to FAA approved rollers. Because of these factorsand/or requirements, only rollers approved by the FAA (Federal AviationAgency) can be used on aircrafts.

The prior art seeks to make a conventional roller lightweight byconstructing the roller as a hollow roller. While using hollow rollersmay help with the weight problem, it creates the additional problem thatthe rollers may more easily become dented or otherwise deformed when auser is rough in loading the cargo. Moreover, hollow rollers allowforeign material, such as dust and dirt to enter the hollow space. Notonly can this interfere with the smooth rolling of the bearings, it canalso increase the weight of the rollers. Metallic rollers, such as thosemade of aluminum and/or steel, through normal use and exposure to theelements, can start to corrode and flake. These flakes can fall into thebearings and cause them to fail, which can lead to further corrosion asbits of metal grind against metal. Further, when the material of theroller, that portion from the outer surface in contact with the load andthe inner surface in contact with the aperture of the roller, becomesthinner, it can weaken the roller to the extent that it may requireweight bearing flanges or supports in order for it to function properly.What is needed is a strong but lightweight, durable roller.

Not only must rollers in the transportation industry be able to bearlarge weights, they must also be able to withstand rigorous handling.When a product moves along the conveyor system, all too frequently, theproduct will get stuck, requiring operator intervention to return theconveyer system to its operation of moving product. Frequently anoperator can manually move the product into line and return the conveyerto operation; however, that is not always the case and sometimes anoperator will resort to tools to move the product so that the conveyercan operate. When large containers of products are on the conveyer andnot moving, frequently an operator will use a pry bar to urge theproduct into the proper location to move the product. Unfortunately,when pry bars are used, the bar is commonly placed between the rollersto lever the product along, the results are frequently denting of theroller housing or otherwise damaging the roller. This problem isexacerbated by the lack of internal support, especially if the rollerwas further hollowed to decrease its weight, and non-resilient materialswere used as in the construction of prior rollers.

Rollers become damaged internally and externally over the course oftheir usable life. Prior rollers were manufactured of metal and providedno mechanism for viewing the internal components of the roller todetermine if the wear had become too extensive for proper operation.Inspection of these rollers would entail disassembly of the rollers,inspection of the interior and reassembly if appropriate. The time andexpense involved in this process have led most users to simply discardrollers after a period of time regardless of the condition of theroller. While the periodic replacement of rollers obviates theinspection costs and repair problems, it is costly to replacefunctioning rollers.

Moreover, manufacture of prior rollers involved assembling various partsincluding bearing, a housing, end caps and other components. Manufactureof a variety of components and later assemblage of the same is costly interms of time and money. The complexity of the process has led to poorlyconstructed rollers.

Again, what is needed is a strong, lightweight roller. The roller mayinclude a mechanism for viewing the structure of the roller for defectsand need for repair. Further, the roller should provide support to thehousing and the housing should be formed of a resilient material forlong life with minimal wear. Additional desired features includecorrosion resistance, ease of manufacture and/or ease of cleaning.

SUMMARY OF THE INVENTION

The present invention is a lightweight roller for a conveyor system withsubstantial new, useful and non-obvious features, which are needed inthe marketplace. Similar to a conventional roller, the roller of thepresent invention is cylindrical having a central aperture for mountingon a conventional axle. In one aspect, the roller is a generallyintegral single piece component formed of suitable polymer. However,unlike conventional rollers, the novel rollers contain lighteningelements on the surface and/or within the roller. Throughexperimentation, the inventors have found that adding these lighteningelements reduce weight, but still allow the rollers to possess theattributes necessary to perform their intended function, conveyingcargo/products in a demanding field. In preferred embodiments, thelightening elements reduce the weight of the rollers, but they do notchange the overall dimensions of the rollers. In preferred embodiments,the lightening elements may reduce the weight of each roller by at least½ a gram. In preferred embodiments, the lightening elements may reducethe weight of each roller by up to half of the original weight of aroller.

In certain embodiments, the lightening elements may be in the form ofcavities located within the material of the roller. These can also bereferred to as internal lightening elements. In other embodiments, thelightening elements may be cavities located on the surface of theroller. These can also be referred to as external lightening elements.The lightening elements may be of various shapes, examples include, butare not limited to, tubular, ovular, circular, semi-circular, divets,and grooves such as straight, curved or zig-zag. In some embodiments,the lightening elements may run lengthwise along the roller,circumferentially, or there may be both elements in a lightened roller.Other applicable shapes will be apparent to those of skill in the art.In still other embodiments, the lightening elements may be locatedwithin the material of the roller and on the surface of the roller.Further, the lightening elements located within the material may belocated wholly within the material creating hollow pockets of variousshapes, and/or they may extend out to the end portions of the rollers.

In the event that the lightening element is located and/or extendedthrough to the end portion of the roller, the lightening element may becovered or plugged to prevent debris from entering the cavity. Acovering may be a film of material such as rubber, paper, or plastic, orplugs of the same to close the lightening elements. One embodiment mayinclude coverings in the form of labels affixed to the ends of therollers to provide the cover for the cavity of the lightening elements.The cover would accommodate the aperture and the shoulders of theroller, if present. Other means will be apparent to those of skill inthe art. In some embodiments, the lightening elements may be filled witha material that weighs less than the material that was removed. Inpreferred embodiments, the lightening elements are unfilled.

The rollers may be constructed as a monolithic unit from a polymericmaterial. The rollers may be molded from a polymeric material. In somepreferred embodiments, the polymer is translucent or transparent toallow visual inspection of the entire roller without disassembly of theconveyor system. In certain embodiments, the rollers may consistessentially of polymeric materials.

The inventive roller may be a lightweight polymeric roller that can beformed from a single piece of a polymer that replaces a conventionalmetallic roller. In its simplest form, the roller is a lightweightpolymeric roller that can be used to replace a conventional roller bysimply removing the axle (also referred to as a shaft) that supports theconventional roller, removing the conventional roller, and replacing theconventional roller with the new lightweight polymeric roller of theproper size and replacing the axle to retain the new roller.

It is an advantage of the invention to provide a lightweight monolithicroller for use in a conveyor or aircraft.

It is another advantage of the invention to provide a dent resistantroller for use in a conveyor or aircraft.

It is a further advantage of the invention to provide a simpleself-lubricating roller that does not require bearings or lubricants foruse in a conveyor or aircraft.

The invention may be a lightweight, one piece roller that includes amechanism for viewing the structure of the roller for defects and needfor repair. Further, the roller provides support to the housing and thehousing is formed of a resilient material for long life with minimalwear. Additional desired features may include corrosion resistanceand/or ease of cleaning.

The lightweight rollers of the invention may be coupled to a conveyorsystem. The lightweight rollers of the invention may be directly orindirectly coupled to a transporting vehicle. In particular, thelightweight rollers of the invention may be directly or indirectlycoupled to an aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b depict two views, a side and an end view,respectively, of one embodiment of the invention.

FIG. 2 depicts another embodiment of the invention.

FIG. 3 depicts an end view of another embodiment of the invention.

FIGS. 4 a and 4 b depict two views, a side and an end view,respectively, of another embodiment of the invention.

FIG. 5 depicts another embodiment of the invention.

FIGS. 6 a and 6 b depict a more detailed view of another embodiment ofthe invention.

FIG. 7 depicts another embodiment of the invention.

FIG. 8 depicts an end view of another embodiment of the invention.

FIG. 9 depicts another embodiment of the invention put into place in anexemplary roller rack.

DETAILED DESCRIPTION

It has been discovered that the rollers of the present invention can bemade lighter through the use of internal and/or external lighteningelements, such as cavities and/or cutouts, while having thecompressibility, impact strength and flexural strength described in theinstant application. These lightweight rollers can handle heavy loads,corrosive environments and abusive treatment such as those found in theair transportation field.

The internal portion (or housing) of the roller is that portion betweenthe outer surface of the roller and the inner surface of the rollerwhich forms the aperture. An internal lightening element resides withinthese two surfaces. FIG. 1 a depicts one example of a roller 110 of theinvention. It shows a roller 110 with an outer surface 112, an innersurface 114, shoulders 116, and an aperture 118, with internallightening elements 150 in the shape of cylinders (tubular). FIG.. 1 bshows an end view of the roller 110. One method of creating theseinternal lightening elements 150 would be to bore through the rolleralong its length similar to the aperture 118. These internal lighteningelements 150 may or may not run the entire length of the roller. It iscontemplated that the internal lightening elements may extend onlypartially into the internal portion of the roller so that weight can bereduced, but leaving the central portions of the roller undisturbed. Acovering, such as a label, can be affixed to the ends of the roller tocover the exposed lightening elements so no debris can settle therein.

The roller 110 may also be molded to have lightening holes 150. Afterthe initial cost to create a mold of the roller 110 (which is moreexpensive than machining from bar stock), it is relatively cheap andfast to produce. Moreover, molding allows for additional variations tothe shape of the lightening elements. For example, as shown in FIG. 5,tubular lightening elements 550 may be created so as not to extend tothe ends of the rollers 510, but rest wholly inside the material/housingof the roller, that portion between the outer surface 512 and the innersurface 514 of the roller 510. This would eliminate the need for a coverfor the lightening elements. Methods of using molds to create productsare well known in the art to the skilled artisan and incorporatedherein.

FIG. 2 depicts another exemplary roller 210. This time the lighteningelements 260 are on the outer surface 212 of the roller 210. They are inthe shape of grooves running circumferentially around the roller 210.These external lightening elements 260, or cutouts, may also beconfigured to help the products they convey stay on their path byreducing the tendency to slip around.

FIG. 3 depicts the end view of yet another exemplary roller 310. Thelightening elements 360 are in the shape of grooves runninglongitudinally along the outer surface 312 of the roller 310. Theseexternal lightening elements 360 may be cut out, such as by lathing, orthey may be molded. Also shown are the shoulder 316, inner surface 314and aperture 318.

Rollers of the invention may include both internal and externallightening elements. They may have at least two lightening elements.Alternatively, the roller may have at least 3, 4, 5, 6, 7, 8, 9, 10, 11,12 or more lightening elements. In one embodiment, such as FIGS. 1 b, 3,and 6, the roller may have two or more lightening elements spaced evenlyabout the aperture. While lightening elements in the shape of tubes orgrooves are easy and quick to create, lightening elements of theinvention are not limited to these, nor are they limited to beingcontinuous. They may be divided into smaller, non-continuous segmentswith the material of the roller found therebetween, such as divets ordimples. Another exemplary roller 410 is depicted in FIGS. 4 a and 4 b(showing the cross sectional view along 1-1) with elliptical lighteningelements 450 found throughout the length of the roller 410. FIGS. 4 aand 4 b show the shoulder 416 and aperture 418. It is also contemplated,as discussed before, that these elliptical lightening elements 450, orother shaped lightening elements, are in the housing (between the outersurface 412 and inner surface 414) and may run continuously along theentire length of the roller, similar to those of FIGS. 1 a and 1 b, theymay run almost the entire length of the roller but not to the ends ofthe roller, or they may be located towards the ends of the rollersleaving the central portion of the roller undisturbed.

It has been found that even a ½ gram alleviation in weight can give aroller an advantage, especially in a cargo hold where there may bethousands of rollers. It is, therefore, contemplated that the lighteningelements reduce the weight of the rollers by at least ½ gram or about0.018 oz. In some embodiments, lightening elements can reduce a roller'sweight (in grams) by at least 1, 1.5, 2, 2.5, 3, 3.5, 4,4.5, 5, 6, 7, 8,9,10,12,14,16, 18, 20, 25, 30, 35, 40, 45, 50, 75,100, 125, 150, 175,200, 250, 300, 350, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900,950, or more. In some embodiments, the roller of the invention mayreduce the weight of a roller, in kilograms, up to 1, 1.25, 1.5, 1.75,2, or more. The corresponding ounces/pounds values will be apparent toone of skill in the art and are not provided herein. In someembodiments, lightening elements may reduce the weight of a roller, inpercentages, by at least 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26,28, 30, 32, 34, 36, 38, 40, or more of its original weight. In someembodiments, lightening elements may reduce the weight of a roller, inpercentages, by up to 42, 44, 46, 48, 50, 52, 54, or more. Generallyspeaking, one factor in the amount of weight that can be reduced whilestill retaining the desirable characteristics of the roller is dependentupon the length and diameter of the roller. Increasing the diameterrelative to the length allows for a larger reduction in weight throughthe use of a bigger and/or increased number of lightening elements.Unlike prior attempts to reduce the weight of rollers by hollowing them,thereby increasing the aperture, lightening elements do not increase thediameter of the aperture of a roller.

Referring to FIG. 5, an exemplary roller 510 is shown having an outersurface 512, an inner surface 514, bushing 532, and an aperture 518.Exemplary tubular internal lightening elements 550 are spaced evenlyabout the aperture 518. The bushing 532, typically found in rollers, maybe integral with the housing, that material from the outer surface 512to inner surface 514 of the roller 510 and may be integral with theshoulder 516. The bushing 532 is shown to extend the entire length ofthe roller 510. Co-axially extending through the bushing 532 is acentrally disposed aperture 518 sized to rotatably receive an axle 520therethrough. The roller 510 can then be secured to a roller rack bypins 522 through the axle (or shaft) 520, thereby either directly orindirectly joining the rollers 510 to a conveyor assembly. In otherembodiments, the shoulder 516 may be a separate piece. If the shoulder516 is a separate piece (may also be called an end cap), it ispreferable that it be made of polymers having suitable physicalcharacteristics for the environment in which the rollers are to operate.Of the voluminous polymers available, suitable polymers includepolysulfone, polyetherimide, polyetherketone, polyphenylene sulfide, andpolyvinylidene fluoride. Other polymers may also work.

The actual size of a roller is dictated by its application. Duringmanufacture, a roller will be constructed to be of a specific length anddiameter to fit a particular application. In general, a roller may beapproximately between ½ inch to 25 feet in length. Preferred rollers maybe, in inches, at least 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5,2.75, 3.0, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 5.0, 5.5, 6.0, or more.Preferred rollers may also be up to, in inches 6.25, 6.5, 7, 7.5, 8,8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28, 30, ormore. In some embodiments, a roller may be between about 0.75 inch to 10inches, about 1 inch to 8 inches, about 1.5 inches to 6 inches, or about2.5 inches to 4.5 inches in length. A roller's diameter may be about0.25 inch to 12 inches. Preferably, its diameter may be about 0.33 inchto 10 inches, about 0.5 inch to 8 inches, about 0.5 inch to 6 inches, orabout 1 inch to 4 inches. As an example only, a roller for an aircraftconveyor may be about 3.25 inches in length and about 1 inch indiameter. An example of the reduction in weight that is possible withlightening elements is that a roller up to 6 inches long and with adiameter of about 3 to 4.5 inches can reduce its weight by up to a ⅓ ofits original weight and still be functional for its intended purpose.

FIGS. 6 a and 6 b depict an exemplary roller 610 of the invention withdimensions. The length of the roller 610 from shoulder 616 to shoulder616 is about 2.55 inches. The length of the outer surface 612 is about2.32 inches measured from one end of the roller 610 to the other. Thechamfer 636 is at a 45-degree angle and is about 0.075 inch in length.The diameter of the shoulder 616 is about 0.62 inch, and the diameter ofthe roller 610 is about 1.5 inches. The lightening elements 650 areabout 0.2656 inch in diameter, and the aperture 618 is about0.3175-0.3225 inch in diameter. These measurements are provided forillustrative purposes only and do not limit the scope of the inventiondisclosed herein.

In another embodiment of the invention depicted in FIG. 7, the bushing732 may not extend the entire length of the roller 710, but extends onlypartially into the central aperture 718 and provides the bearing surfaceproximate the ends of the roller 710 to receive the axle 720 (notshown). Internal lightening elements 750 extend only partially into thematerial at both ends of the roller 710, leaving the center portionintact. A shoulder 716 is formed on each end of the roller 710. Theshoulder 716 can provide a small space between the outer periphery ofthe roller (the ends) and the arms of the roller rack to minimize thepossibilities of materials catching therebetween and fouling the roller710. In this embodiment, it has been found that sufficient bearing areais provided, and the removal of the central part of the bearing does notadversely affect the longevity of the roller 710.

In still another embodiment depicted in FIG. 8, the end of the roller810 may be bored to accept a bearing 834. The bearing 834 may be any ofthe numerous types of readily available bearings, such as a ballbearing, roller bearing, needle bearing, or the like. Bearings 834 ofthis type are well known in the art and readily available from numeroussources. Although it is not required, the bearing 834 may be a sealedbearing. The bearing 834 is set into the end of the roller 810 leavingthe bearing extending slightly out from the end of the roller 810 sothat the bearing may perform the same function as the shoulder 716 ofthe roller 710 shown in FIG. 7.

The material making up the housing of the roller should have acompressibility strength sufficient to allow the roller and aperture toremain generally round as cargo passes over the conveyor. Should theroller or aperture become overly distorted, the rollers will not rotateand will impede the movement of product or cargo along the conveyor. Ithas been found that a compressibility strength of 20 psi or greater issuitable for aircraft conveyor systems. Desirably, a roller of theinvention may have a compressibility strength of at least 20, 50, 100,200, 500, 1000, 2000 psi or greater when the roller is used in aircraftconveyors. The compressibility strength causes the roller to either loseor retain shape as weight bears on the roller.

Loosely related to the compressibility strength is brittleness. Rollerscommonly receive sudden shock loads or other jarring force, such as fromdropped loads or shifting loads or weights from sudden acceleration anddeceleration. In these situations, it is important that the roller doesnot chip or otherwise deform. It has been reported that an impactstrength needs to remain at or above 0.5 foot lbs./inch. Desirably, theimpact strength will be 1.0 ft. lbs./inch or greater. It has been foundthat workers using conveyors use pry bars and other similarly shapedtools prying against the rollers to dislodge stuck product. This makesimpact strength important to guard against sudden shock loads that mayoccur in such instances.

The material of the roller should further be sufficiently resilient toreturn to its original shape after the cargo passes over the roller.Typically, the rollers are used millions of times over the life span ofthe roller. Rollers commonly wear by becoming misshaped over the life ofthe product. It has been reported that rollers should have a flexuralstrength of 20 psi or greater. Rollers of the invention may have aflexural strength of at least 20, 50, 100, 200, 500, 1000, 2000 psi orgreater. A higher flexural strength adds life to the roller by providinga lower tendency to deform and a higher tendency to return to itsoriginal shape.

A method of testing the functionality of these rollers is by conductinga distributed load test for compressibility strength. Variouslaboratories are available to test the rollers. In essence, the rollerto be tested is placed in a fixture that supports the roller by the pinshaft on either side. The fixture/roller assembly is placed beneath thecrosshead of a calibrated universal testing machine, such as the TiniusOlson universal testing machine, MM210-002, such that a solid hexagonalrod would apply force along the length of the roller. The hexagonal rodmay have a diameter of 1.07 inches and each face may measure 0.6 inchwide. The rod contacts the roller along its entire length. Force isapplied to the roller through the hexagonal rod at a rate of 0.5 inchper minute. A load versus deflection chart is plotted during each test.The point at which the load deviates from the initial straight-lineportion of the curve is noted as the yield load. Testing continues untilthe roller has clearly yielded.

The ultimate strengths of rollers in terms of compressibility, impactstrength, and flexural strength are dependent upon their intended use.The strengths set forth above are generally applicable to thetransportation industry, in particular to their use in aircrafts.

The rollers of the invention may be constructed of known materials.Preferably, the materials are polymeric. Polymeric materials areparticularly amendable to accommodating lightening elements. It has beenfound that various readily available polymers are suitable forfabrication into rollers. Suitable preferred polymers includepolysulfone, nylon, polycarbonate, polyetherimide, polyetherketone,polyphenylene sulfide, and polyvinylidene fluoride and acetylcopolymers. Acetyl copolymers are readily available under the trademarksof CELCON®, ACETRON®, and other trademarks from various vendors.

Particularly relevant to the airline industry, rollers must be able topass a burn test to be FAA approved. Acetyl copolymer, an exemplarypolymer, has been subjected to a burn test and has passed. The burn testis set forth in the FAA guidelines. The burn test requires that a rollerhave a burn rate of less than 4.0 inches per minute. The test sampleshave shown a burn rate of 0.6 inch per minute.

While the acetyl copolymer rollers do not have the tested strength ofsome prior art metal rollers, the strength is sufficient for theintended uses. Moreover, acetyl copolymer rollers, as well as otherpolymers, lend themselves well to accommodating lightening elements.Notable too was that, when tested against prior metal rollers that werehollowed to reduce weight, acetyl copolymer rollers of similar weightdid not dent or deform. Further, during compression experimentation,when an acetyl copolymer roller did fail, the failure was obvious tosee, allowing for easy detection and replacement. This ability wouldallow for quick detection of damaged rollers when these rollers are putto use in conveyor systems.

When the bushing is integral to the housing as shown in FIG. 5,lubricity is helpful to allow turning of the roller 510 on the axle 520.In such cases, a polymeric roller is desirable as lubricity may becontrolled by the selection of an appropriate polymer. Should thepolymer not have natural lubricity, lubricity may be added via alubricant compatible with the chosen polymer. Also, polymeric bushingsare more resistant to spalling bushing particles into the environment.Examples of suitable bushing materials include various polymers such asNYLON®, DELRIN®, and acetyl copolymers; or various alloys of brass andbronze, including OILITE®.

Polymeric rollers also allow for considerations of lubricity to be givento the outer surface 512 of the roller 510, as the choice of polymerscan help prevent product or cargo atop the conveyor from moving tooquickly or slowly. Polymeric rollers also tend to last longer than metalrollers. In some industries, cargo is moved along rollers on a largemetal tray. With metal rollers, the metal-to-metal contact eventuallycauses wear leading to flaking of metal particles into the surroundingareas. This debris can find its way into the bearings of rollersreducing their efficiency or causing them to fail, and eventually makingits way into the aperture of the roller. Not only can this buildup ofdebris affect the ability of the rollers to rotate properly, it can alsoincrease the weight of the rollers. Polymeric rollers are resistant tothis type of damage, increasing the useful life of the roller.

Manufacturing one of the exemplary rollers such as FIGS. 1 a and 1 b, 4,and 6 may be made simple by machining an elongate piece of round stockto a suitable diameter, boring the stock to create a central apertureand lightening elements, cutting to length and detailing the ends tosuit. A label may be affixed to the ends of the roller designed to coverthe exposed lightening elements while leaving uncovered the centralaperture to receive the axle. Surprisingly, it is efficient to machinerollers from readily available round stock. The machining may beautomated on any of a number of CNC machines such as the HardingeSUPERSLANT™ and others.

Other means of manufacturing rollers include molding or injectionmolding. A moldmaker (toolmaker) constructs a mold of the roller withthe desired dimensions and features including the lightening elements. Amold usually consists of the longitudinally half of a roller. Thematerial of the roller, preferably a polymer, is melted and injectedinto the molds. Once set, two halves of a roller are bound together tomake a complete roller. The inventive rollers are not dependent on themanner of manufacture. Variations on methods of manufacturing rollers ofthe invention will be apparent to those of ordinary skill in therelevant art.

Lightening elements may be left empty, or they may be filled with alightweight filler. One such filler may be a lighter aerated version ofa polymer used for the roller. Another possible filling might be alightweight polymer different from the one used to make the roller. Yetanother possibility is the use of foamed polymers, including open orclosed cell foams. The lightening element may be closed or covered witha film, cap, or plug. In other embodiments, the lightening element maynot be closed. In still other embodiments, the lightening element may befound wholly inside the material at the ends of the roller. In otherwords, the lightening element does not extend to the ends of the roller.

In its use, an exemplary roller 910 with lightening elements 950, asshown in FIG. 9, of the correct size is selected for installation intoan application. The roller 910 has shoulders 916 and covers 952 for theinternal lightening elements 950. Typically, a group of rollers isinstalled as a unit called a roller tray. A roller tray consists of amultiplicity of roller assemblies 940 (roller and roller rack). Theselected roller 910 is taken to the roller assembly for installation.The existing roller is first removed by removing the retaining pin 922and sliding the axle 920 from the roller rack 942, freeing the oldroller. A new roller 910 is placed between the arms 946 of the rollerrack and above the base 944 of the roller rack. The axle 920 is thenpassed through an arm 946 of the roller rack and through the centralaperture 918 of the roller 910 and finally through the second arm 946 ofthe roller rack 942. The retaining pin 922 is then replaced and the newroller 910 has been installed.

After installation, a new roller 910 functions as the previousconventional roller had functioned. Product is rolled over the roller910 and, perhaps, stored on the roller 910. A user may move the productover the rollers 910 and secure the product in a suitable location. Whennecessary the product may be forcibly moved either by the user orthrough the use of tools such as pry bars.

Periodically, the rollers may be inspected visually. With translucent ortransparent rollers, a quick simple visual inspection will detect anydamage to the roller obviating the need for an inspector to crawl aroundon the rollers inspecting to discover damage to conventional rollers.However, even with an opaque roller of the invention, any internaldamage to a roller can usually be readily detected by a visualinspection of the surface of the roller.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize changesmay be made in form and detail without departing from the spirit andscope of the invention.

What is claimed:
 1. An aircraft roller comprising: a) a cylindricalbody, said body having a length and diameter; b) an aperture extendinglongitudinally along and through the center of said body; and c) atleast two lightening elements.
 2. The aircraft roller of claim 1,wherein the lightening elements are internal.
 3. The aircraft roller ofclaim 2, wherein a shape of the internal lightening element is selectedfrom the group consisting of tubular, ovular, elliptical, or spherical.4. The aircraft roller of claim 1, wherein the lightening elements areexternal.
 5. The aircraft roller of claim 4, wherein a shape of theexternal lightening element is selected from the group consisting oftubular, circular (circumferential), semi-circular, divets, and groovessuch as straight, curved or zig-zag.
 6. The aircraft roller of claim 1,wherein the body of the roller comprises a polymer.
 7. The aircraftroller of claim 6, wherein the polymer is selected from a groupconsisting of polysulfone, nylon, polycarbonate, polyetherimide,polyetherketone, polyphenylene sulfide, and polyvinylidene fluoride andacetyl copolymer.
 8. The aircraft roller of claim 6, wherein the polymeris acetyl copolymer.
 9. The aircraft roller of claim 1, wherein thelightening element reduces the weight of a roller by at least ½ a gram.10. The aircraft roller of claim 1, wherein the lightening elementreduces the weight of a roller by at least 10 grams.
 11. The aircraftroller of claim 1, wherein the roller has a compressibility strength ofat least 20 psi.
 12. The aircraft roller of claim 1, wherein the rollerhas an impact strength of at least 0.5 foot lbs./inch.
 13. The aircraftroller of claim 1, wherein the lightening element is unfilled.
 14. Theaircraft roller of claim 1, wherein the roller is coupled to a rollersystem.
 15. An aircraft roller comprising: a) a cylindrical body, saidbody having a length and diameter, wherein the body is made of apolymer; b) the cylindrical body having two ends; c) an apertureextending longitudinally along and through the center of said body; d)at least two internal lightening elements extending longitudinally aboutthe aperture; and e) a covering affixed to the ends of the body to coverthe lightening elements.
 16. The aircraft roller of claim 15, whereinthe polymer is acetyl copolymer.
 17. An aircraft roller system having atleast one operable roller unit comprising: a) at least one roller beingcylindrical in shape and having a length and a diameter, a centeraperture extending through the length of the roller and at least onelightening element; b) an axle having a diameter sized to rotatably fitwithin the central aperture of the roller, the axle further having aretention mechanism located upon the axel ends; c) an elongate “U”shaped roller rack, the roller rack sized to extend the length of theroller and having a pair of upwardly extending arms located adjacent theends of the roller, each arm end having an aperture sized to receive therespective axle end and locate the axle and roller in a fixed location.18. The aircraft roller system of claim 17, wherein the roller is madeof a polymer.
 19. The aircraft roller system of claim 18, wherein thepolymer is selected from a group consisting of polysulfone, nylon,polycarbonate, polyetherimide, polyetherketone, polyphenylene sulfide,and polyvinylidene fluoride and acetyl copolymer.
 20. The aircraftroller system of claim 18, wherein the polymer is acetyl copolymer.